1. Field of the Invention
This invention relates to an electrophoresis gel sheet used for carrying out electrophoresis of a substance having an electric charge in a solution, like protein or nucleic acid, in an electrophoresis apparatus used for separation, analysis or the like of the charged substance on the basis of the electric charge and the molecular weight thereof.
2. Description of the Prior Art
There has heretofore been known an operation of electrophoresis by which separation and analysis of charged molecules of protein, nucleic acid, their decomposition products, or the like, by utilizing migration of the charged molecules under the effect of an electric field are effected. For this purpose, various electrophoresis suporting media, for example, supporting media comprising polyacrylamide gel, agarose gel, or the like supported between the non-conductive plates or the polymer films, are used.
Particularly, in the biotechnology (genetic engineering) which has attracted attention in recent years, the electrophoresis operation is indispensable for determining a base sequence in the molecule of nucleic acid such as DNA fragment by utilizing autoradiography.
In the case where the operation of electrophoresis is carried out by use of the electrophoresis supporting medium (hereinafter referred to as a gel sheet) comprising two polymer films and polyacrylamide gel, agarose gel, or the like supported between the polymer films, the gel sheet is supported by being sandwiched between electrically non-conductive glass plates having predetermined thicknesses (not smaller than 3 mm) and loaded in this form into an electrophoresis apparatus in order to secure the gel sheet and to prevent exposure to an ionizing radiation emitted by diffused molecules migrating through the gel. At this time, if the gel sheet is supported between the glass plates with dust or the like intervening between the glass plates and the thin polymer films constituting the surfaces of the gel sheet, the gel portion where dust or the like is present is distorted together with the thin polymer films by the dust or the like, in the width direction and in the thickness direction, even though the dust or the like is very small and has a diameter of, for example, within the range of several microns to several tens of microns. Since the very small dust or the like clings to the surfaces of the polymer films constituting the gel sheet by electrostatic attraction given rise to on the surfaces of the polymer films, it is almost impossible to remove the clinging dust or the like completely. When the operation of electrophoresis is carried out with the gel being distorted by the dust or the like, it is difficult to obtain a normal pattern of migration bands, the migration pattern often being distorted. In the case where the operation includes the procedure of comparing multiple rows of the migration pattern in the width direction of the gel sheet as in the operation for determining the base sequence of DNA fragment, the distortion of the migration pattern results in low reliability of the information obtained on the base sequence in DNA fragment or the like. specifically, the migration speed of DNA fragment or the like under electrophoresis becomes uneven due to changes in the thickness of the gel membrane and the distortion of the gel while DNA fragment or the like passes through the gel portion where the thickness of the gel is uneven. As a result, the distortion of the migration pattern such as oblique bands or zigzag bands arise. If DNA fragment or the like under electrophoresis is once subjected to such a history, DNA fragment or the like continues to migrate in such distorted condition, even though the gel portion through which DNA fragment or the like passes thereafter is free from distortion.